I have two items that use 1" bolts, one is ASTM A325 and the other is ASTM A449, I would like to just use one. Which is the one that meets or exceeds the other?
These bolts are identical with regard to strength and chemistry. There are very minor differences in the hardness requirements, but the proof load, tensile, and yield strength requirements are the same. From a manufacturing standpoint, we make these bolts using the same raw material and the same heat treating and production methods. Our strength by grade chart gives a detailed comparison.
The difference between these two specifications (A325 and A449) is the diameter range, configuration, and application. A325 bolts are heavy hex head bolts ONLY, and are designed for structural steel connections. They range in diameter from ½” – 1-1/2” inclusive. Due to their application, an A325 structural bolt has a shorter thread length than a typical heavy hex bolt. If you need a bolt with longer threads, ASTM A449 should be used.
ASTM A449 bolts range in diameter from ¼” – 3” inclusive and are far more flexible in their configuration. In other words, A449 bolts can be a headed bolt, a straight rod with threads, or a bend bolt such as a right angle bend foundation bolt.
With regard to availability, A325 bolts are mass produced and far more common in the marketplace than A449 bolts. Therefore, A325 bolts would be immediately available and considerably less expensive than A449 bolts, unless the bolts you are dealing with are exceedingly long in length. Since the thread length on A325 bolts is very short you should make sure they will be adequate for your application. ASTM suggests using A449 in lieu of A325 when a nonstandard thread length is needed. Here is an excerpt from the A325 specification:
This specification is applicable to heavy hex structural bolts only. For bolts of other configurations and thread lengths with similar mechanical properties, see Specification A 449.
For example, a 1” diameter A325 bolt that exists in the marketplace will have 1-3/4” of thread. There is a supplemental requirement in the A325 specification for fully threaded A325-T bolts that are 4 X diameter in length or shorter. There are often 1” diameter fully threaded A325’s that are readily available but they are no longer than 4” in length.
Portland Bolt’s position regarding ASTM specifications are that they are simply guidelines. They provide a buyer with a reasonable expectation as to the product they will receive if they order it to an ASTM specification. However, if the buyer and seller agree to change any portions of the specification, that is acceptable as long as the change is clear and agreed upon by both parties. Therefore, we frequently manufacture A325 bolts with longer thread lengths than “standard”. Since 1” diameter A325 bolts wouldn’t exist “on the shelf” with that nonstandard thread length anyhow (2-3/8”), it would make more sense to spec the bolt to A449 since it would be the proper spec to use and the bolts would need to be manufactured special regardless of which specification you choose.